Patent EA-004072-B1 (EA)
Title: A device for encoding/decoding n-bit source words into corresponding m-bit channel words, and vice versa
Inventor: KAHLMAN JOSEPHUS A H M
IPC: H03M7/14
Filed: 2001-04-02
Abstract: 1. A device for encoding a stream of data bits of a binary source signal into a stream of data bits of a binary channel signal, wherein the bit stream of the source signal is divided into n-bit source words, which device comprises converting means adapted to convert said source words into corresponding m-bit channel words, characterized in that each value of the n-bit source words together with another value of the n-bit source words forms a pair of source words, the values of the source words of said pair of n-bit source words differ in the bit values of the q<TH> bits in the n-bit source words, q being a constant, the pairs of n-bit source words being subdivided into a first part and a remaining part, and the converting means are adapted to convert n-bit source words into m-bit channel words, in such a manner that the conversion of the two source words forming a pair of source words of the first part of the pairs of n-bit source words is parity preserving and the conversion of the two source words forming a pair of source words of the remaining part of the pairs of n-bit source words is parity inverting. 2. A device as claimed in claim 1, characterized in that the converting means are adapted to convert a block of p consecutive n-bit source words into a corresponding block of p consecutive m-bit channel words, where n, m and p are integers, m>n>=2, p<=1, and where p can vary. 3. A device as claimed in claim 2, characterized in that m=n+1. 4. A device as claimed in claim 3, characterized in that n=2. 5. A device as claimed in claim 4, characterized in that the device is adapted to convert single source words into corresponding single channel words in accordance with the following Table: Source word Channel word SW1 00 SW1 101 SW2 01 SW2 100 SW3 10 SW3 000 SW4 11 SW4 001 6. A device as claimed in claim 4 or 5, wherein the converting means are adapted to convert 2-bit source words into corresponding 3-bit channel words, so as to obtain a channel signal in the form of a (d,k) sequence, where d=1, the device further comprising means for detecting the position in the bit stream of the source signal where encoding of single 2-bit source words into corresponding single channel words would lead to a violation of the d-constraint at the channel word boundaries and for supplying a control signal in response to said detection, characterized in that, in the absence of the control signal, the converting means are adapted to convert single 2-bit source words into corresponding single 3-bit channel words. 7. A device as claimed in claim 6, wherein, in the presence of the control signal, which occurs during the conversion of two consecutive source words, the converting means are adapted to convert a block of said two consecutive 2-bit source words into a block of two corresponding 3-bit channel words, in such a manner that one of the two source words in the block of source words is converted into a 3-bit channel word which is not identical to one of the four channel words CW1 to CW4, in order to preserve the d=1 constraint, characterized in that, in the presence of said control signal, the converting means are further adapted to convert the block of said two subsequent 2-bit source words into a corresponding block of two subsequent 3-bit channel words,. 8. Device as claimed in claim 1 or 7, characterized in that the converting means are adapted to convert blocks of two consecutive 2-bit source words into blocks of two consecutive 3-bit channel words in accordance with the coding given in the following Table: Block of 2 source words Block of 2 channel words 00 00 100 010 00 01 101 010 11 00 000 010 11 01 001 010 9. A device as claimed in claim 6, 7 or 8, where k has a value larger than 5, the device being further having means for detecting the position in the bit stream of the source signal where encoding of single 2-bit source words into single 3-bit channel words would lead to a violation of the k-constraint and for supplying a second control signal in response to said detection, characterized in that, in the presence of the second control signal, which occurs during the conversion of three consecutive 2-bit source words, the converting means are adapted to convert a block of said three consecutive 2-bit source words into a block of corresponding three consecutive 3-bit channel words, the converting means are further adapted to convert two of the three source words in the block into corresponding 3-bit channel words not identical to the four channel words CW1 to CW4, in order to preserve the k constraint. 10. A device as claimed in claim 1 or 9, characterized in that the converting means are adapted to convert blocks of three consecutive 2-bit source words into blocks of three consecutive 3-bit channel words in accordance with the coding given in the following Table: Block of 3 source words Block of 3 channel words 10 10 10 000 010 010 10 10 11 001 010 010 01 10 11 101 010 010 01 10 10 100 010 010 11. A device as claimed in any one of the preceding claims, characterized in that the conversion means are adapted to perform a signal processing operation upon the binary source signal, which operation is equivalent to the conversion of consecutive source words into consecutive channel words, followed by an aT-precoding of said channel words. 12. A device as claimed in claim 1 or 11, characterized in that it further comprises bit-adding means for adding one bit to subsequent blocks of r bits of the source signal. 13. A device as claimed in any one of the preceding claims, characterized in that it further comprises means for recording the stream of data bits of the binary channel signal in a track on the record carrier. 14. A method of encoding a stream of data bits of a binary source signal into a stream of data bits of a binary channel signal, wherein the bit stream of the source signal is divided into n-bit source words, the method comprising the step of converting said source words into corresponding m-bit channel words, characterized in that each value of the n-bit source words together with another value of the n-bit source words forms a pair of source words, the values of the source words of said pair of n-bit source words differ in the bit values of the q<TH> bits in the n-bit source words, q being a constant, the pairs of n-bit source words being subdivided into a first part and a remaining part, and the converting step comprises the conversion of n-bit source words into m-bit channel words, in such a manner that the conversion of both the two source words forming a pair of source words of the first part of the pairs of n-bit source words is parity preserving and the conversion of the two source words forming a pair of source words of the remaining part of the pairs of n-bit source words is parity inverting. 15. A record carrier provided with a binary channel signal, which binary channel signal has been obtained by conversion of a corresponding binary source signal, wherein the bit stream of the binary channel signal has been divided into m-bit channel words, the binary source signal has been divided into n-bit source words and the m-bit channel words have been obtained by conversion of the n-bit source words into corresponding m-bit channel words, characterized in that each value of the n-bit source words together with another value of the n-bit source words forms a pair of source words, the values of the source words of said pair of n-bit source words differ in the bit values of the q<TH> bits in the n-bit source words, q being a constant, the pairs of n-bit source words being subdivided into a first part and a remaining part, the conversion of the n-bit source words into m-bit channel words being such that the conversion of the two source words forming a pair of source words of the first part of the pairs of n-bit source words is parity preserving and the conversion of the two source words forming a pair of source words of the remaining part of the pairs of n-bit source words is parity inverting. 16. A record carrier provided with a 1T-precoded channel signal, which 1T-precoded channel signal has been obtained by 1T-precoding of a binary channel signal, which binary channel signal has been obtained by conversion of a corresponding binary source signal, wherein the bit stream of the binary channel signal has been divided into m-bit channel words, the binary source signal has been divided into n-bit source words and the m-bit channel words have been obtained by conversion of the n-bit source words into corresponding m-bit channel words, characterized in that each value of the n-bit source words together with another value of the n-bit source words forms a pair of source words, the values of the source words of said pair of n-bit source words differ in the bit values of the q<TH> bit in the n-bit source words, q being a constant, the pairs of n-bit source words being subdivided into a first part and a remaining part, the conversion of the n-bit source words into m-bit channel words being such that the conversion of the two source words forming a pair of source words of the first part of the pairs of n-bit source words is parity preserving and the conversion of the two source words forming a pair of source words of the remaining part of the pairs of n-bit source words is parity inverting. 17. A device for decoding a stream of data bits of a binary channel signal into a stream of data bits of a binary source signal, wherein the bit stream of the channel signal is divided into m-bit channel words, which device comprises deconverting means adapted to deconvert m-bit channel words into corresponding n-bit source words, characterized in that each value of the n-bit source words together with another value of the n-bit source words forms a pair of source words, the values of the source words of said pair of n-bit source words differ in the bit values of a q<TH> bit in the n-bit source words, q being a constant, the pairs of n-b